In response to RFA-AA-12-006, this application proposes the UCSD Research Component of the National Consortium on Alcohol and Neurodevelopment in Adolescence (N-CANDA) to determine the effects of alcohol use on the developing adolescent brain. Recruited at ages 12 through 21, a high risk enhanced community sample of 170 San Diego subjects (N=680 from all 4 sites) will complete a baseline assessment and undergo three annual follow-up assessments in an accelerated longitudinal design. At each visit, a multimodal magnetic resonance imaging (MRI) protocol, comprehensive neuropsychological battery, and assessments of alcohol and other substance use and related problems, mental health symptomatology, and substance use disorder risk factors will be measured. Brain imaging includes state-of-the-art high-resolution structural MRI (sMRI), diffusion tensor imaging (DTI), and resting state MRI (rsMRI). The examination of alcohol consequences will focus on structural and functional maturation of brain areas that actively develop during adolescence, are involved in psychological regulation, respond to rewards, and appear vulnerable to neurotoxic effects of alcohol. In addition, our Research Component will collaborate on two additional studies. First, we will collaborate with the Duke University site to study recovery of these abnormalities. Specifically, we will examine the degree to which targeted heavy drinking related neurocognitive and brain integrity deficits remit over 4 weeks of monitored abstinence. Second, we will collaborate with the SRI International site to study the default mode network. In particular, we will examine the influence of adolescent heavy drinking on default mode network integrity, and the extent to which this mediates cognitive performance, using functional connectivity analyses during a Stroop Match to Sample task in conjunction with resting state fMRI data acquired both before and after the task. Studied in the context of risks and baseline brain characteristics, we will determine both the effects of alcohol exposure on the developmental trajectory of the adolescent human brain, and identify preexisting psychobiological vulnerabilities that may put an adolescent at elevated risk for an alcohol use disorder.